An improper or indecent description which makes a receiver feel unpleasant may be included in a junk mail transmitted from a malicious trader. If an electronic mail filtering program such as an anti spam filter is installed in a terminal of the receiver, it is possible to select this kind of junk mail from among all electronic mails which are received by the terminal and to delete it. In the electronic mail filtering program, words which are frequently included in junk mail are provided as a database. A CPU of the terminal which is installed with such an electronic mail filtering program checks words included in an electronic mail with the database when the electronic mail is received, and determines that the electronic mail is a junk mail in a case where the same words as those recorded in the database are included in the electronic mail with a predetermined number or more. Details of a process which is performed by the CPU according to this kind of electronic mail filtering program are disclosed in Patent Document 1, for example.